Precious metal recovery process from carbonaceous ores

ABSTRACT

A process for recovering at least one precious metal from an ore containing carbonaceous material is disclosed. The process involves the use of certain plant derived ortho-quinone containing components, in particular, certain lignin and/or tannin derived components containing ortho-quinone functionality. 
     Preferred compositions comprise at least one ligno sulfonate component containing ortho-quinone functionality. In the process, the use of at least one additional oxidant capable of maintaining the ortho-quinone containing functionality in the desired oxidation state provides for integrated process synergy.

RELATED APPLICATIONS

This application is a continuation in part of copending application Ser.No. 936,237 filed Aug. 26, 1992, which is a continuation-in-part ofco-pending application Ser. No. 751,793 filed Aug. 29, 1991, which is acontinuation-in-part of co-pending application Ser. No. 627,896 filedDec. 13, 1990 now abandoned which application is a continuation ofapplication Ser. No. 213,884 filed Jun. 30, 1988 now abandoned whichapplication is a continuation-in-part of application Ser. No. 005,130filed Jan. 20, 1987, now U.S. Pat. No. 4,765,827 and application Ser.No. 025,069, filed Mar. 12, 1987, now U.S. Pat. No. 4,801,329. Each ofthese applications and patents are hereby incorporated in their entiretyherein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a process for recovering at least one metal,e.g., gold, silver, the platinum group metals and the like, from an orecontaining carbonaceous material and the metal to be recovered. Inparticular, the invention relates to a process which involves processinga metal-containing ore so as to facilitate the recovery of the metalfrom the ore.

Carbonaceous ores, i.e., ores which contain elemental carbon (e.g.,graphite) and/or organic compounds, often contain valuable metals, suchas gold, silver, the platinum group metals and the like. Onecharacteristic of such ores which has made them difficult and expensiveto process is that the presence of carbon and organic compounds inhibitsmetal recovery using conventional, e.g., cyanide, processing. In otherwords, the presence of organic material in such carbonaceous ores tendsto interfere with metal extraction, e.g., by cyanidation. For example, asubstantial amount of carbonaceous ore is not amenable to conventionalcyanidation techniques because of the presence of carbon (which oftenacts like activated carbon), and relatively long chained organichydrocarbon-type compounds containing sulfur, nitrogen, carboxylic acidgroups and the like.

There is a growing world-wide interest in metal recovery fromcarbonaceous ores. Thus, in spite of the substantial work which has beendone to provide for such metal recovery, a need currently exists toprovide for a process for metal recovery from carbonaceous ores.

SUMMARY OF THE INVENTION

A process for recovering at least one metal from an ore containing themetal and at least one of certain carbonaceous material has beendiscovered.

In one broad aspect, the present process involves contacting at leastone ore containing at least one metal to be recovered and carbonaceousmaterial with at least one added plant derived aromatic component havingortho quinone functionality in an amount effective to at least promotethe oxidation of the carbonaceous material. The contacting occurs atconditions effective to (1) chemically oxidize at least a portion of thecarbonaceous material, and (2) at least partially liberate the metal tobe recovered from the ore. By liberation is meant that the gold is moresusceptible to recovery, for example by cyanidation, than withoutpretreatment. The first metal is then recovered from the ore.

In one embodiment, the contacting occurs in the presence of anadditional oxidant, more preferably a gaseous source of oxygen, e.g.,air, enriched/diluted air, oxygen and the like.

In one embodiment, the plant derived aromatic containing componenthaving ortho quinone functionality is preferably selected from acomponent which has one or more water solubilizing groups attached tothe component more preferably as a water soluble salt such as an alkalimetal salt. The plant derived aromatic containing component havingortho-quinone functionality, hereinafter referred to as ortho-quinonecomponent, and mixtures thereof is present in an amount effective to atleast promote the oxidation of the carbonaceous material. The ore orores preferably contain precious metals, such as gold, silver, theplatinum group metals and the like, which can be recovered using theprocess of this invention. The various embodiments of this invention canbe practiced singly or in any combination of embodiments, with selectionand optimization generally being a function of the ore type and desiredmetal value recovered.

The benefits resulting from the process of this invention, e.g.,improved rate of oxidation including solubilization and/or conversion toa different form, i.e., solids, such as insoluble jarrosite, sulfates,arsenates and the like, improved rate of oxidation of the carbonaceousmaterial and/or yield/recovery of desired metal as a function of time,are substantial. Without wishing to limit the invention to any specifictheory of operation, it is believed that many of such benefits resultfrom the direct and/or indirect oxidation, i.e., oxidation promotingeffect of one or more of the above o-quinone containing components inthe process of this invention on the carbonaceous portion of the ore. Itis believed that the effect of the ortho-quinone containing component isan oxidation effect which reduces the affinity of the carbonaceousmaterial for gold complexes, particularly gold cyanide complexes, whichaffinity (referred to in the art as preg robbing) reduces and/orsubstantially reduces the recovery of gold from such ores. It isbelieved that the o-quinone containing components can interact directlyand/or indirectly with the carbonaceous material by direct oxidation ofthe carbonaceous material and/or by the generation of an active oxidantspecie which interacts with the carbonaceous material to reduce its pregrobbing characteristics.

Another embodiment of this invention is the obtaining of such benefitsthrough a catalytic effect by the ortho-quinone containing components.Without wishing to limit the invention to any specific of operation, itis believed that the ortho-quinone containing component during itsoxidation interaction with the carbonaceous material is reduced and issubsequently regenerated by an additional oxidant such as an activeoxygen specie, such as oxygen. During a given period of time in whichthe ore is contacted with the ortho-quinone containing component and anadditional oxidant, the ortho-quinone containing component can cyclebetween an oxidized and reduced state, i.e., the component isregenerated, thereby allowing the oxidation of the carbonaceous materialto be carried out with an amount of ortho-quinone containing componentless than would be required without the regeneration of such component.The use of such lesser amounts of the ortho-quinone containingcomponent, i.e., a catalytic amount, allows for improved processefficiencies.

The promoting effect of the presently useful ortho-quinone redox couplesallows the process to be effective, e.g., from the standpoint ofimproved recovery of desired metal as a function of time, on a widevariety of difficult to process ores.

Improved yields or recoveries of metal are often achieved under lesssevere conditions by practicing the present process, especially whencompared to recovering metal from the carbonaceous ore without utilizingthe process of this invention. The present process is relatively easy tooperate and control. Relatively low concentrations of the o-quinonecontaining components are used and relatively mild operating conditionsmay be employed. With regard to carbonaceous ores, operating and capitalcosts are often reduced relative to previous chlorination/oxidationprocedures which require substantial amounts of chemicals and/orexpensive metallurgy to combat corrosion problems. Thus, the presentinvention can provide a cost effective approach to metal recovery fromcarbonaceous ores.

DETAILED DESCRIPTION OF THE INVENTION

The present process provides substantial advantages. For example, theuse of at least one of certain promoting o-quinone containingcomponents, particularly lignin and tannin derived componentsparticularly having water solubilizing groups such as the sodium saltand more particularly in a redox cycling catalytic amount in thepresence of an additional oxidant provides for improved contacting,e.g., to increase the rate of carbonaceous material oxidation andultimately to improve the yield of metal or metals recovered. Theimproved rate of carbonaceous material oxidation also results insignificant process and cost economies. In addition, effective metalrecoveries can be achieved utilizing low grade (heretofore difficult toprocess) carbonaceous ores. Further, the present process does notrequire the addition of sulfur dioxide or hydrogen sulfide to maintainor culture any bacteria.

The process of the present invention is useful for metal recovery fromcarbonaceous ores, as defined herein. A large number of ore bodies andlarge amounts of carbonaceous ores are susceptible to be treated inaccordance with the present process. Examples of such ores include:oxidized and carbonaceous ores from various locations in north centraland northeastern Nevada, such as the Carlin ore, the Cortez ore and theWitwatersrand ore; ores from the Prestea and Ashanti gold fields inGhana; the Natalkinsk and Bakyrichik ores from the Soviet Union; variousCanadian ores such as the gold ore from the Mcintyre Mine, located nearSchamacher, Ontario; and the like ores. The carbonaceous ores mayinclude oxidized ore material, possibly even a major amount of oxidizedore material. Also, the carbonaceous ores may contain metal pyrites. Thecarbonaceous ore which contains metal pyrites may be processed forpyrite removal by physical and/or chemical means to reduce the pyritecontent of the ore prior to the contacting step of the present inventionor be processed along with the carbonaceous portion of the ore. Forexample, subjecting the ore to various procedures such as grinding,particle size fractionation, flotation and the like can reduce theamount of metal pyrites in the ore.

The present process employs at least one of certain o-quinone containingcomponents. Such components may include alkali and/or alkaline earthmetals and/or ammonium salts provided that they also contain o-quinonecontaining functionality which is effective in the present invention.Such o-quinone containing components are present during the contactingstep in an amount effective to at least promote the oxidation of thecarbonaceous material in the ore, Thus, such ortho quinone containingcomponents are present in an amount effective to promote such oxidationand/or to oxidize the carbonaceous material in the ore.

The presently useful plant derived aromatic components having o-quinonefunctionality are preferably selected from the group consisting of oneor more lignin derived components, one or more tannin derived componentsand mixtures thereof. The lignin and tannin derived components may beselected from natural materials or lignin and tannin containingmaterials from various lignin and tannin manufacturing processes. As setforth above, preferred components having ortho-quinone functionality arethose that also have water solubilizing functionality particularly as awater solubilizing salt particularly at alkaline pH.

Lignin in higher plants is formed by complex enzymatic processes whichproduce substituted phenolic compounds. Lignins are a family ofthree-dimensional polymers which bind together the cellulose fibers inhigher plants. Lignins can provide rigidity to the plant structure and,being in general resistant to chemical and biological attack, helpsplants from decay. Lignin is distributed widely throughout the plantkingdom. Plant lignins are generally divided into three broad classeswhich are commonly called softwood, hardwood and grass or annual plantlignins. The latter also includes such plants as bamboo and palm. Thuslignin can be released by chemical or mechanical disintegration from awide variety of plant tissues including, as set forth above, softwood(coniferous), hardwood (deciduous) or from bark, cambium, sapwood orheartwood. In addition, lignin can be released from jute, rice hulls,peanut shells, barley straw, begasse, coconut shells, alfalfa, pineneedles, oat and wheat straw, corn cobs and various other plantmaterials.

Although the exact structure of lignin is unknown, plant lignins fromcertain trees are considered to be a polymeric material almost entirelymade up of phenylpropane units that exist as branched chains ofcross-linked structures. In lignin from softwood trees, nearly all thearomatic rings have one methoxyl group in position three from the propylside chain.

The phenolic precursors of hardwood lignin trees contain methoxyl groupsin one or both of the positions adjacent to the phenolic hydroxyl;however, in softwoods the precursors are generally substituted at onlyone position and occasionally not at all. As a result of this softwoodlignin contains about twice as many reactive sites on the aromatic ringsand contain a higher proportion of carbon--carbon linkages betweenaromatic rings. A chemical structure which incorporates various chemicalgroupings found in, for example, spruce native lignin in their existingratios shows various joined coniferyl units with approximately one-thirdof the units still having a free phenolic group and most having analiphatic alcohol group in the side chain. A majority of the phenolicgroups are generally in etherified form, i.e., a phenolic polyether, andhave a number average molecular weight of generally about 2000 to about10,000.

There are two major pulping processes which promote lignin solubility,each using a different approach. In sulfite processes, the ligninmolecule is attacked by sulfonate anions generally in the presence ofsodium, ammonium, magnesium or calcium cations and at varying pH valuesto produce a range of pulps with varying lignin and hemicellulosecontents. The lignin molecule in this process becomes sulfonated andthus water soluble. Alternatively, in alkaline processes, the ligninmolecule is depolymerized by alkaline hydrolysis of the ether bondsbetween the aromatic units.

Lignosulfonate products are generally produced from wood by the acidbisulfite pulping process and the kraft process. In the acid sulfitepulping process, the lignin in, for example, wood chips is subjected toreaction with an aqueous bisulfite salt at elevated temperature andpressure. During the process, the lignin is rendered water-soluble by acombination of depolymerization and sulfonation. Both cleavage andsulfonation occur almost entirely at positions immediately adjacent tothe aromatic rings. Cleavage of this carbon-oxygen bond destroys one ofthe linkages common to both hardwood and softwood lignin.

The resulting lignin sulfonate is dissolved in the spent sulfite pulpingliquor along with a variety of carbohydrate compounds which areprimarily formed by degradation of the hemicellulose components of wood.The chemical composition of hemicellulose varies considerably withspecies of tree, even within the general categories of hardwoods andsoftwoods. The degradation products, therefore, also vary widely and caninclude glucose, mannose, galactose, xylose, arabinose and rhamnose inproportions which are determined largely by the wood source. Thesesugars usually account for 20-25% of the total spent sulfite liquorsolids. In addition, ash can be present in the liquor solids.

In sulfite pulping, generally up to about one-half of the coniferylbuilding units of the lignin molecule add sulfonate groups with varyingease. The locations of the attacks are generally the highly activebenzyl alcohol or benzyl ether groups of the lignin. These oxygencontaining groupings on the carbon adjacent to the aromatic ring arevery labile and are substituted in the pulping process by the highlypolar sulfonate groups. If the benzyl alcohol or ether is attached to afree phenolic unit, a sulfonate group is more readily introduced thanwhen the benzyl group is attached to a phenol ether. Sulfonationapparently also occurs on side chain carbons adjacent to carbonylgroups. Thus, through addition of solvating groups to the high polymerlignin and through low order acid hydrolysis and splitting of the ligninmolecule, solution of the lignin is achieved.

Lignosulfonates are generally classified as polydisperse macromolecularpolymers with molecular weights ranging from several hundred to morethan one hundred thousand. The phenylpropane structural units oflignosulfonates can be linked together in many different patterns bycarbon-carbon and ether linkages. Most of the sulfonate groups inlignosulfonates are thought to be joined to the alpha carbons of theside chain, with about one sulfonate radical for two phenylpropaneunits. Primary hydroxyl groups are found on many of the phenylpropaneunits while others have various carbonyl groups.

Lignosulfonates from the sulfite process can generally have a weightaverage molecular weight up to about 100,000. The calcium lignosulfonatecan be used as starting materials for other products due to the easewith which the calcium cation may be replaced with other cations to formthe appropriate soluble sulfate salts, such as sodium, ammonium andpotassium.

The other basic process to solubilize lignin is the alkaline pulpingprocesses. The most predominate lignin interlinkage is the beta ethertype, and this is cleaved by alkali to form smaller molecular sizephenols which tend to dissolve in water as the sodium phenolate salts.In phenyl coumarin type interlinkages, alkali attack frees the phenolicgroup for solubilizing salt formation, but concurrent formaldehyde lossfrom the side chain can produce a double bond between the two benzenerings to form phenolic stilbene portions in the alkali lignin.

In the kraft process, pulping liquor which contains from about 20 toabout 30 wt % sodium sulfide in a mixture with sodium hydroxide is used.Whereas, sodium hydroxide alone will depolymerize the lignin to solubleform, the hydroxide can also split the ether groups of the woodcarbohydrates causing their undesired dissolution. A sodiumhydroxide-sodium sulfite mixture is generally more effective inachieving continued lignin dissolution while having comparable effectson the carbohydrate dissolution. Apparently, sulfide not only promotesmore rapid splitting of the lignin ether groups, but introduction ofsulfur in the benzyl alcohol position may inhibit concurrentpolymerizing reactions.

The location of the alkaline attack on the native lignin generallyresults in the ether groups being split to form smaller molecular sizefree phenols. Typically about 5 to 10% of the lignin can be decomposedall the way down to monomeric phenols in the liquor, while the remainderis solubilized as higher molecular weight portions of the gross ligninmolecule. The potential ether split and loss of formaldehyde can producestilbene type structures. Comparable dehydration and formaldehyde losscan produce unsaturated ethers. In addition, carboxyl groups are alsofound in kraft lignin.

In alkaline hydrolysis, the phenolic group in the lignin molecule aregenerally doubled so that they are present on a majority of the units.

By proper two-stage acidification, coagulation and purification, therecan be obtained a reproducible kraft lignin from pine black liquor witha structure and number average molecular weight approximately about 2000to about 12,000 and a weight average molecular weight of about 2500 toabout 10,000. Based upon the mode of alkaline attack, a generalizedstructure can be designated as a plurality of aromatic units aspolyelectrolyte with phenolic groups, carboxyl groups, keto groups,aliphatic hydroxyl, and double bonds.

The processed lignin can be further processed to modify variousproperties of the lignin such as solubility in an aqueous medium, forexample, by substituent group modifications such as sulfonic, hydroxyl,polyhydroxyl and further reactions with polyhydroxy aromatic compounds,particularly catechol containing compounds. Such modifications,including examples as set forth above, are included within the scope ofthis invention.

Lignin derived products can undergo physical and chemical modificationby modification of sulfite liquor, sulfonated lignin, and kraft lignin.Depending on the optimum properties required, lignin derived products,including lignosulfonates, can be processed by one or more methodsincluding conversion to other salts, polymerization, classification ofmolecular weights, and oxidation-reduction of macromolecules. Thesolubility, absorption, electrolytic, and complexing characteristics ofsuch products can be modified based upon their molecular structure shapeand size, i.e., the type, quantity and location of functional groupsincluding sulfonic, sulfonate, sodium sulfonate, hydroxyl, poly hydroxyincluding di hydroxy benzene such as catechol, carbonyl, methoxy,carboxyl and chloride.

As set forth above, the preferred lignin derived products havingortho-quinone functionality are those having water solubilizing groups,particularly sulfonate, carboxylate, phenolate groups and the like whichenhance the solubility characteristics of such components particularlyat alkaline pH. In addition, it is preferred to optimize the amount ofortho-quinone functionality in the lignin containing component,preferably during processing such as during the sulfite or kraft pulpingprocess. During such processing, catechol functionality is believed tobe introduced by demethylation during the depolymerization and/orhydrolysis and other reactions of the lignin raw material. The formationof catechol functionality is believed to be enhanced by both temperatureand alkaline pH particularly at increased process severities. As setforth above, the lignin containing component can be further reacted toenhance the formation of catechol functionality. The catecholfunctionality can be converted to the ortho-quinone functionality using,for example, an active oxygen species, such as oxygen. As used herein,the term plant derived aromatic containing components includes bothcomponents having ortho-quinone functionality and/or catecholfunctionality which can be converted to ortho quinone functionality,preferably under the in situ and external regeneration processconditions of this invention. In addition, various substituent groupscan be introduced onto the 1,2 dihydroxy benzene functionality group inorder to modify the oxidation potential and regeneration of the reducedortho-quinone functionality for overall effectiveness in the treatmentof the carbonaceous ore. In general, substituents on the quinone nucleussuch as halogens particularly chloride, CN, So₃ Na in general raise thepotential of the ortho-quinone functionality, whereas alkyl, i.e.,methyl, methoxy, hydroxy, and various amine and alkyl substituted aminegroups in general decrease the oxidation potential. As set forth above,the optimum oxidation potential and the oxidizing power of theortho-quinone component is a function of the carbonaceous portion of thecarbonaceous ore, the process conditions particularly the pH, and theregeneration of the ortho-quinone component, whether such regenerationbe in situ such as when the ortho-quinone component is utilized incatalytic amounts or when larger amounts of the ortho-quinone componentare utilized. The ortho-quinone component can be regenerated, forexample, externally and recycled to the process. In general, it ispreferred to have an oxidation potential of the ortho-quinonefunctionality which allows for reasonable process efficiencies, i.e.,oxidation of the carbonaceous portion of the ore, so as to improveoverall precious metal liberation and to provide ease of regenerationfor the continued oxidation of the carbonaceous portion of the ore insitu and/or external regeneration.

Typical examples of lignin derived products which are suitable toprovide the o-quinone oxidants of this invention are, for example, thetreated or untreated spent liquors (i.e., containing the desiredeffluent lignin product solids)obtained from wood or other plantconversion, for example, the waste pulp liquor, or modified ligninproducts, such as by pyrolysis, reduction modification or ozonation ofthe aforementioned lignin individual products including spent liquors.The alkaline oxidized, hydrolyzed, partially desulfonated andsubsequently resulfonated lignosulfonates are also suitable.

Certain of these lignin containing components are obtained in wastepulping liquors derived from softwood and hardwood starting materials.Lignin containing components may be additionally sulfonated orsulfomethylated.

Other lignin containing products are the ozonated lignosulfonatesobtained from ozonation of the aforementioned ligno products, includingtreated or untreated spent liquors. In addition, purified lignincontaining products from which the sugars and other saccharideconstituents have been partially or totally removed such as byfermentation or, additionally, inorganic constituents have also beenpartially or totally removed are also useful.

As a further alternative, the lignin containing components may be one ofthe desulfonated lignosulfonates (including substantially purelignosulfonate compositions) which are generally obtained bycatalytic--frequently alkaline--oxidation processes conducted underconditions of high temperature and pressure, oftentimes withaccompanying hydrolysis.

As set forth above, further modification of the lignin derived productsare included within the scope of this invention and include the reactionof the foregoing lignin containing product materials with, for example,a halide, a halocarboxlyic acid or a sulfonating agent. In addition,further reactions can include one or more combinations of alkoxylation,sulfation, alkoxysulfation, alkylation or sulfomethylation. Any suitablesulfonation reagents may be used for sulfonation reaction. When straightsulfonation is desired, it is advantageously accomplished with an alkalimetal (such as sodium) sulfite or sulfur dioxide. Sulfoalkylation can beaccomplished with mixtures of an appropriate lower alkyl aldehyde and abisulfite.

Other lignin containing compounds which may be used in the practice ofthis invention are the derivatives of an oxidized, partiallydesulfonated lignosulfonate obtained in the spent oxidized liquor from adilute vanillin oxidized softwood or hardwood, spent sulfite liquor byacidification prior to vanillin extraction with an organic solvent andwhich can be further treated with, for example, sodium bisulfite and analdehyde, preferably formaldehyde, at elevated temperature tosulfoalkylate, and/or sulfomethlate, the desulfonated lignosulfonatemolecules.

Tannins occur in many plants and are in general separated by extraction.A typical example of tannin compound includes tree bark extract such asquebracho, hemlock and redwood extracts. The tannins are aromatic andare obtained from various plants and trees. Particularly preferredtannins are the condensed tannins which have catechol functionality,i.e., the catechol tannins which can generate and/or be converted toortho-quinone functionality.

As set forth above, the activity (regeneration)of the o-quinonecontaining component can be affected by the pH of the aqueouscomposition employed in the present contacting step. Some activity ofthe o-quinone component may have to be sacrificed because of the pH ofthe aqueous composition during the contacting, which pH may be preferredfor various other processing reasons. The particular pH employed canalso affect the salt form of the o-quinone containing componentemployed, and such salts are o-quinone containing components within thescope of this invention.

As set forth above, the ortho-quinone containing components areeffective in a catalytic and/or promoting amount, particularly in thepresence of an additional active oxidant species such as oxygen, andsuch combination of component plus additional oxidant allows theortho-quinone containing component to cycle between an ortho-quinonefunctionality and a reduced catechol functionality. Thus, theortho-quinone containing component can interact with the carbonaceousportion of the ore followed by regeneration, i.e., reoxidation of thecatechol functionality. After regeneration, the ortho-quinonefunctionality can further interact with the carbonaceous portion of theore. Thus the ability to rapidly cycle between the ortho-quinone andcatechol states produces a cycling component which can oxidize and beregenerated, thereby producing a series of oxidations/regenerationsduring contacting of the ore. As set forth above, the ortho-quinonecontaining component can be modified such as through substituent groupson the aromatic ring to optimize activity for both oxidation andregeneration, i.e., effective oxidation of the carbonaceous ore witheffective regeneration, preferably rapid regeneration. The optimizationprovides for overall improved process effectiveness. Thus substituentgroups such as methoxy, sulfonate, hydroxy, chloride and cyanide can beused to modify and enhance the overall oxidation regenerationeffectiveness of the ortho-quinone containing components. Thus, it ispreferred that the ortho-quinone containing component cycle rapidly andproduce a number of cycles, for example at least about 4 cycles andgenerally from about 5 cycles up to about 1000 cycles or more or up toabout 100 cycles, the number of cycles in general being such numberwhich effectively allows for an improvement in metal recovery from thecarbonaceous ore. The number of cycles in general will be a function ofthe carbonaceous content of the ore, its preg robbing characteristics,the concentration of the ortho-quinone containing component, as well asother impurities and components in the ore which may be susceptible tooxidation. By the term "cycle" is meant a single oxidation regenerationcycle, commonly referred to in promoter catalyst terms as "oneturnover."

The specific amount of the o-quinone containing component employed mayvary over a wide range and depends, for example, on the carbonaceous oreand/or the o-quinone containing component employed, and on the degree ofoxidation desired. The weight percent of o-quinone functionality, basedupon the molecular weight of the ortho-quinone component, can vary overa wide range and in general represents a weight percent of from at leastabout 1 weight percent to about 40 weight percent of the weight of theortho-quinone containing component, i.e., for those compounds containingortho-quinone functionality, more preferably from at least about 2 toabout 30 weight percent and still more preferably from at least about 5weight percent to about 25 weight percent. By ortho-quinonefunctionality is meant an ortho-quinone functionality having a molecularweight of about 108 and the relationship of that molecular weight from aweight percent standpoint to the total molecular weight of the compound.For example, for certain components the total molecular weight can berepresented by the total molecular weight of the phenyl propane units,including substituents or such phenyl propane units. Since theortho-quinone containing components in general will be mixtures, theabove preferred ranges apply to the individual ortho-quinone containingcomponents within the mixture.

Preferred molecular weight ranges are from about 1500 to about 75,000,more preferably from about 2000 to about 10,000 and still morepreferably from about 2000 to about 6000.

In certain embodiments, preferred concentrations of the ortho-quinonecontaining component are in the range of about 0.05 to about 3%, morepreferably from about 0.1 to about 2% by weight based upon the aqueouscomposition employed in the contacting, calculated as o-quinonecontaining component. It is generally convenient to provide theo-quinone containing compound in combination with, preferably insolution in, the aqueous composition used in the contacting step. As setforth above, it is preferred that the ortho-quinone containing componentbe present in an effective catalytic and/or promoting amount,particularly within the ranges set forth above. In addition, as setforth above, it is preferred that the ortho-quinone containing componentbe water soluble at the concentration and conditions at which it iseffective for carrying out the process of this invention.

The o-quinone containing component can be added to the contacting stepand/or can be formed in situ prior to or in the course of thecontacting.

The present contacting preferably takes place in the presence of anaqueous liquid medium or composition. The ortho-quinone containingcomponent, which is preferably soluble in the aqueous medium, may beadded to the aqueous medium prior to the contacting. Any suitable,aqueous medium can be employed in the present process, including saltsolutions, preferably sodium chloride. The pH of the aqueous medium mayvary and in general a neutral or basic medium, preferably a basic oralkaline medium can be employed depending, for example, on thecomposition of the ore or ores being treated, the specific ortho-quinonecontaining component being employed, and the presence or absence ofother components or entities such as soluble metals during thecontacting. Preferably, the pH of the aqueous composition is in therange of about 7 to about 13, preferably from about 9 to about 13 and,still more preferably, from about 10 to about 12. The pH of the aqueousmedium may be adjusted or maintained, e.g., during the contacting step,for example, by adding acid and/or base.

The aqueous medium comprises water, preferably a major amount of water.The medium is preferably substantially free of ions and other entitieswhich have a substantial detrimental effect on the present process. Anysuitable acid and/or base or combination of acids and/or bases may beincluded in, or added to, the medium to provide the desired pH. Forexample, hydrogen halides, preferably hydrogen chloride, sulfurous acid,sulfuric acid, metal salts which decompose (in the aqueous medium) toform such acids, alkali metal hydroxides, for example, sodium andpotassium, alkaline earth metal hydroxides, ammonium hydroxide, metalsalts which decompose (in the aqueous medium) to form such bases, theircorresponding carbonates, preferably sodium carbonate, mixtures thereofand the like may be employed. It is preferred to use an hydroxide as thebase, preferably sodium hydroxide. The quantity and composition of theaqueous medium may be selected in accordance with the requirements ofany given ore to be treated and as may be found advantageous for anygiven mode applying the present process in practice. In carrying out thepresent process, one or more wetting agents and/or sulfur dispersionagents and/or metal catalysts can be included in, e.g., added to, theaqueous composition (in addition to the ortho-quinone containingcomponents) to further enhance rates and/or yields. Examples of suchagents include hydrocarbon sulfonates, lignosulfonates, alkylsubstituted succinic anhydrides, alcohol ethoxylates and the like.Typical examples of metal oxidation catalysts are iron, copper, cobalt,vanadium, and manganese components which are soluble in catalyticallyeffective amounts in an aqueous medium, preferably selected from ironcomplexes with ligands, copper complexes with ligands, vanadiumcomponents with ligands, manganese components with ligands, and mixturesthereof.

The amount of ortho-quinone containing components employed may varywidely provided that such amount is effective to function as describedherein. Such ortho-quinone containing components are preferably presentduring said contacting in an amount less than about 5%, more preferablyin the range of about 0.05% to about 3% by weight, and still morepreferably from about 0.1% to about 2%, calculated as o-quinonecontaining material, based on the amount of ore present and/or liquidpresent during contacting such as a solution used in an agitated leachor during a vat or heap leach. One of the substantial advantages of thepresent process is that large amounts of ortho-quinone containingcomponents are not required although adjustments can be made dependingon the deleterious carbon concentration in the ore. Thus, in order toreduce costs still further while achieving benefits of the presentinvention, low concentrations of such materials are preferably selected.

The present contacting is preferably conducted in the presence of atleast one additional active oxidant species other than the ortho-quinonecontaining component. The oxidant is present in an amount effective todo at least one of the following: maintain or form the ortho-quinonecontaining component, produce or regenerate at least a portion of theortho-quinone containing component, and/or oxidize at least a portion ofthe carbonaceous material in the ore. The oxidant or oxidants may bepresent during the contacting step and/or during a separate step to formand/or regenerate the ortho-quinone containing component. Any suitableoxidant capable of performing one or more of the above-noted functionsmay be employed. The oxidant is preferably selected from the groupconsisting of molecular oxygen (e.g. in the form of air, dilute orenriched air, or other mixtures with nitrogen or carbon dioxide), singleoxygen, ozone, inorganic oxidant components containing oxygen and atleast one second metal and mixtures thereof. More preferably, theoxidant is selected from the group consisting of molecular oxygen,oxidant components containing oxygen and at least one second metal andmixtures thereof. Still more preferably, the oxidant is oxygen. Theoxidant can involve a mixture of oxidants such as an oxidant componentcontaining oxygen and at least one second metal, and molecular oxygen inan amount effective to maintain the ortho-quinone containing componentin the desired oxidized state and/or to oxidize at least a portion ofthe carbonaceous material in the ore and/or in the case of a reduciblemetal oxidant, to reoxidize such oxidant by, for example, molecularoxygen. Care should be exercised to avoid large excesses of the oxidantto as to minimize reactions that could solubilize deleterious elements,i.e., arsenic, etc.

The reducible second metal oxidants useful in the present invention maybe chosen from a wide variety of materials. The second metal or metalsare preferably not the same as the metal or metals to be recovered fromthe ore or ores. Preferably, the second metal is a metal which formsreducible metal oxides which are reduced during the conduct of theprocess of this invention. Many of the transition metals have thisproperty. Typical examples of metals which have this property includeminerals and other compounds which are generally solids under thecondition of the process, such as, manganese, tin, lead, bismuth,germanium, antimony, indium and certain of the rare earth metals andminerals, e.g., cerium, praseodyminium and terbium and mixtures of rareearth minerals which typically have varying ratios of lanthanum, cerium,etc. Such reducible second metal components are preferably capable ofbecoming at least partially reduced at the present contacting conditionsto form a reduced second metal component.

Manganese is a more preferred second metal. In one embodiment, thereducible manganese component includes manganese in the 4+ oxidationstate. One particularly useful reducible manganese component ismanganese (manganic)dioxide and its pyrolusite, manganite, birnessiteand manganese-bearing minerals from the spinel group. Silver,manganese-containing ores in which at least a portion of the silver islocked by the manganese-bearing minerals are particularly useful incombination with ores containing carbonaceous material, as describedherein. In the above embodiment, it is preferred to have presentmolecular oxygen during processing. The latter system providessubstantially soluble components for recovery of metal.

The present contacting results in at least a portion of theortho-quinone containing component being chemically reduced to form areduced di hydroxy benzene containing component. This reduced componentcan exit the contacting zone and be separated from the ore or ores, inparticular the contacted ore or ores, i.e., partial to substantialseparation. This component can be used on a once-through basis, or maybe regenerated to an ortho-quinone containing component as set forthabove, in situ or externally and recycled to the contacting zone. In thecase of a once-through basis, it is preferred to minimize the amount ofreduced component exiting with the ore or ores. Such regeneration can bedone by oxidizing the reduced component or with molecular oxygen, insitu or external, at ambient and/or elevated temperatures to convert thereduced component to an ortho-quinone containing component.

The amount of oxidant employed in the present invention is chosen tofacilitate the desired functioning of the present contacting step.Without limiting the invention to any specific theory or mechanism ofoperation, it may be postulated that when oxidant is employed suchoxidant acts in conjunction with the ortho-quinone containing componentto oxidize at least a portion of the carbonaceous material in the oreand "liberate" the metal to be recovered from the ore. Although theortho-quinone containing component takes an active part in the oxidationand liberation functioning, when oxidant is employed, such ortho-quinonecontaining component preferably acts as a catalyst or promoter and maybe, and preferably is, used more than once in the present contactingstep, e.g., is recycled to the present contacting step or is employed tocontact more than one increment of the ore or ores.

The amount of oxidant employed preferably acts to facilitate the desiredoxidation of the reduced ortho-quinone containing component andoptionally at least a portion of the carbonaceous material andliberation of metal to be recovered from the ore. The specific amount ofoxidant employed varies depending on many factors, for example, thespecific ore or ores being treated, the specific ortho-quinonecontaining component and oxidant being employed, and the specific degreeof oxidation and metal liberation desired. If a reducible second metaloxidant is used, it preferably is used in an amount in the range ofabout 0.1% or less to about 10% or more to about 150% by weight of themetal sulfide or deleterious carbon content of carbonaceous ore.Preferably, the amount of oxidant employed in the present contactingstep should be sufficient to provide the oxidation/metal liberation tothe desired degree. Substantial excesses of additional oxidant should beavoided since such excesses may result in materials separation andhandling problems, and may result in reduced recovery of the desiredmetal or metals.

Although one or more of the oxidants may be utilized in a separateoxidation or regeneration step, it is preferred that such oxidants, andin particular oxygen, be present and effective during the contactingstep of the present invention.

The contacting of the present invention takes place at a temperature andpressure and for a time sufficient to obtain the desired results. Acombination of temperature and pressure effective to maintain water (theaqueous medium)in the liquid state is preferred. In one embodiment,temperatures of about 20° to about 140° C. with temperatures in therange of about 20° C. to about 110° C. and in particular between about23° C. to about 60° C. being especially useful. Contacting pressure maybe in the range of about atmospheric to about 500 psia or more.Pressures in the range of about atmospheric to about 100 psia have beenfound to provide satisfactory results.

Contacting times vary widely depending, for example, on the mode inwhich the contacting is performed. Such contacting time may range fromminutes to weeks or even months. For example, if the contacting occursin a stirred tank with the ore or ores present in a slurry with theaqueous medium and the ortho-quinone containing component, thecontacting time preferably is in the range of about 0.1 hours to about60 hours, more preferably about 1 hour to about 24 hours. On the otherhand, if the contacting takes place with the ore or ores placed in aheap with the aqueous medium and ortho-quinone containing componentbeing made to flow through the heap, the contacting time is preferablyin the range of about 1 day to about 6 months, more preferably about 7days to about 60 days.

The present process may be conducted on a batch or continuous basis. Thepresent contacting step may be conducted on a pad, with the ore or oresto be treated situated in a heap; or in a vat, tank or other suitablearrangement. The primary criterion for the contacting step is that thedesired carbonaceous material oxidation and metal liberation take place.Preferably, the metal-containing carbonaceous ore and the ortho-quinonecontaining component are brought together to form an intimate admixturegenerally with the aqueous composition. The ore or ores are preferablysubjected to particle size reduction, e.g., by crushing, grinding,milling and the like, prior to contacting to render the ore or ores moreeasily and/or effectively processed in the present contacting step. Airor other gaseous oxidant may be dispersed through, or otherwisecontacted with, this admixture during the contacting step to achieve thedesired result. Amounts of acid and/or base and/or can be added to theinitial admixture and/or may be added during the contacting to providethe desired pH.

The pH of the aqueous liquid medium may be adjusted or maintained duringthe contacting step, for example, by adding one or more basic componentsto the aqueous liquid medium. Any suitable basic component orcombination of such components may be included in, or added to, thismedium to provide the desired basicity. For example, basic alkali metaland alkaline earth metal components, e.g., hydroxides, silicates,carbonates and bicarbonates, mixtures thereof and the like may beemployed. Because of cost, availability and performance considerations,calcium hydroxide, sodium hydroxide, and mixtures thereof, particularlysodium hydroxide, are preferred.

The solid ore/material remaining after the contacting step may besubjected to any suitable metal recovery processing step or steps forthe recovery of the metal, e.g., silver, gold, the platinum group metalsand the like. For example, this solid ore/material may be neutralizedwith any suitable acidic or basic material, such as sulfuric acid,carbonates, bicarbonates white lime or milk of lime, and then subjectedto a conventional sodium cyanide extraction, followed by activatedcarbon treatment and zinc dust precipitation. Alternately, the solidore/material after contacting can be neutralized and subjected to anammonium thiosulfate or an acid thiourea extraction followed by zincdust precipitation. Still further, the solid ore/material aftercontacting can be subjected to a brine extraction followed by ionexchange to recover the desired metal or metals. The conditions at whichthese various recovery processing steps take place are conventional andwell known in the art, and therefore are not described in detail here.However, it is important to note that conducting the metal recoveryprocessing on the ore/material after the contacting of the presentinvention provides improved metal recovery performance relative toconducting the same metal recovery processing without this contacting.

In a further embodiment of this invention the contacting step and metal,e.g., silver, gold, platinum group metals and the like, recovery stepcan be practiced at the same time in the same processing system, i.e.,agitated, vat or heap. The pH of both systems should be similar to avoidany deleterious side reactions e.g., destruction of the cyanide solutionor thiourea. For example, the ortho-quinone containing components whichare effective at higher pH's, preferably the ranges set forth above,more preferably, e.g., about 9 to about 13, can be used in the presenceof cyanide leaching solution to provide both liberation and recovery ofmetals in the same system.

One processing arrangement which provides outstanding results involvesthe agglomeration of, for example, the metal-containing carbonaceous oreand a solid ortho-quinone containing component. The ore, ores and/ormaterials are preferably subjected to crushing, grinding, or the likeprocessing to reduce particle size to that desired optimum metallurgicalliberation, generally a maximum particle diameter of about 1/2 inch orless. The solid particles are mixed with sufficient aqueous. Thisintimate admixture is formed into agglomerates by conventionalprocessing, such as agglomeration, extruding, pilling, tableting and thelike.

The agglomerates are placed on a pad, to form a heap which is built upby addition of agglomerates, preferably over a period of time in therange of about 15 days to about 60 days. During the time the heap isbeing built up, and preferably for a period of time ranging up to about3 months, more preferably about 2 months to about 3 months after thelast agglomerates are added to the heap, an aqueous compositioncontaining the ortho-quinone containing component and preferablyadjusted for pH, and/or the presence of air, is made to flow through theheap, e.g., from the top to the bottom of the heap. After contacting theheap, the aqueous composition is collected and processed for disposal;or processed for ortho-quinone containing component recovery,regeneration and/or recycling to the heap. This contacting providesanother important benefit in that at least a portion of the"cyanacides," such as copper, which may be present in the ore and/ormetal sulfide-containing material can be removed and/or deactivated.Such "cyanacides" cause substantial increases in cyanide consumption ifpresent in cyanide extraction processing. Therefore, removing and/ordeactivating cyanacides in the present contacting step provides for moreeffective metals recovery by cyanide extraction.

Following contacting with the ortho-quinone containing component aqueousmedium, a dilute aqueous cyanide, preferably sodium cyanide, solution ismade to contact the heap. Typically, this cyanide contacting isperformed in the presence of air. Preferably, the cyanide solution ispercolated through the heap. The cyanide solution, after being contactedwith the heap, contains the metal or metals to be recovered. Thissolution is collected and sent to conventional further processing forrecovery of the metal or metals. As set forth above, both ortho-quinonecontaining component and cyanide contacting can be conductedconcurrently.

The heap is preferably maintained at ambient conditions e.g., oftemperature and pressure. Also, a heap may be built up and worked(contacted) with the aqueous composition and the cyanide solution for aslong as the economics of the particular application involved remainfavorable.

When an agitated leach in vessels is used for the process, contact timesmay vary depending, for example, on the specific ore or ores beingcontacted, the other components present during the contacting and thedegree of metal recovery desired. Contact times in the range of about 5minutes or less to about 48 hours or more may be used. Preferably, thecontact time is in the range of about 4 hours to about 36 hours, morepreferably from about 8 hours to about 24 hours. During this time,agitation can be advantageously employed to enhance contacting. Knownmechanical mixers can be employed. As set forth above, the ortho-quinonecontacting component and cyanide contacting can be conductedconcurrently.

As set forth above, cyanidation can be used to recover precious metalvalues, particularly gold and silver, from ores containing such preciousmetal values. In the cyanidation process, alkaline cyanide solution aremixed with liberatable and/or amenable gold and silver ores to dissolvethe metal values from the ore. In the dissolution reaction, the preciousmetal, for example gold (solid), reacts with the cyanide ion in thepresence of oxygen and water to form a gold cyanide complex. One of theproblems with aeration using air dissolved in the aqueous solution atambient or elevated pressures in for example agitated or heat bleachesis the non-uniform distribution of the oxygen and, in general, very slowreaction kinetics. Various approaches to improve overall efficienciesfor the required oxidant has been the use of pure oxygen and theaddition of hydrogen peroxide for the oxidant used in forming the goldcyanide complex. In a further embodiment of this invention, it has beenfound that the ortho-quinone containing component can function as anoxidant in cyanidation to improve and enhance the recovery of preciousmetals, particularly gold and silver. In carrying out the cyanidationprocess, the ortho-quinone containing component interacts with the goldand cyanide solution to form a gold cyanide complex. The precious metalsare then recovered by conventional precious metal recovery processes asset forth above. The ortho-quinone component interaction with the goldand cyanide solution can be direct and/or indirect oxidation, i.e.,promoting oxidation, optionally in the presence of oxygen. Thecombination of ortho-quinone containing component and aqueous cyanidesolution provides for improvements in, for example, the overall recoveryof precious metal and/or the rate at which the gold cyanide complex isformed in comparison to conventional processing such as aeration. Thecyanidation process of this invention is applicable to a wide range ofprecious metal containing ores including carbonaceous ores, sulfidecontaining ores, oxide ores, as well as other ores, particularly oreswhich are amenable to cyanidation for recovery of precious metals,

The following non-limiting examples illustrate certain of the advantagesof the present invention.

EXAMPLE I

A quantity of a high carbonaceous ore was selected for bench scaletesting. The experiment employed 1000 grams of ore (75% minus 65 mesh)which produced 33 weight percent solids of an aqueous fraction. Thesystem was agitated with air sparging and suspended in a water bathmaintained at 50° C. The conditions and results of this experiment issummarized as follows:

Conditions: The aqueous fraction included 1.0% by weight of a sodiumlignosulphonate which had been produced by an acid bisulfite pulpingprocess. The sodium lignosulphonate had been processed to reduce thereducing sugar content to 0.1 wt/percent. The lignosulphonate furtherhad the following chemical properties: 16.1% sodium, 0.5% calcium, 1.5%sulphate sulfur, 2.5% wt/pct non-sulphonate sulfur, 8.9% sulphonatesulfur, 11.4% total sulfur, 4.5% methoxy, and contained catecholfunctionality. Prior to the addition of the sodium lignosulphonatecomponent, a 45 wt/% aqueous solution of the sodium lignosulphonate wassparged with air at a temperature of 35° C. for a period of time of 30minutes at a pH of 12 adjusted with sodium hydroxide. The air spargingoxidized residual catechol functionality to the orth-quinonefunctionality. The aqueous fraction was adjusted to a pH of 11.5 to 12and the process was continued for a period of 24 hours in a stirredreactor with air sparging. The ore was analyzed as containing largequantities of carbonaceous material and had a gold content of 0.051ounces per ton. The gold recovery by conventional cyanidation after 72hours based on Head vs Tail Analysis was 57.8%.

Results: The ore after processing was subjected to cyanidation in thesame manner as the untreated ore and a gold recovery of 77.8% wasachieved.

These results show the outstanding effectiveness of an ortho-quinonecontaining component of this invention for the recovery of gold from ahighly carbonaceous ore. The example also shows the cyclic activity ofthe ortho-quinone containing component with oxygen to provide enhancedgold recovery.

While the present invention has been described with respect to variousspecific examples and embodiments, it is to be understood that thepresent invention is not limited thereto and that it can be variouslypracticed within the scope of the following claims.

What is claimed is:
 1. A process for recovering at least one first metalselected from the group consisting of gold, silver, the platinum groupmetals and mixtures thereof from an ore containing carbonaceous materialcomprising contacting said ore with a least one added plant derivedaromatic component selected from the group consisting of lignin, andtannin and having ortho-quinone functionality wherein the ortho-quinonefunctionality is present in the component in the range of from at leastabout 1 weight percent to about 40 weight percent of the total weight ofthe plant derived aromatic component and mixtures thereof said plantderived aromatic component being present in an aqueous soluble amount toat least promote the oxidation of at least a portion of saidcarbonaceous material and at least partially liberate the metal to berecovered from said ore and an additional oxidant being present toprovide at least one of the following: (1) form and cycle to an oxidizedstate said plant derived aromatic component between ortho-quinone andcatechol oxidation states and (2) cycle to an oxidized state said plantderived aromatic component between ortho-quinone and catechol oxidationstates and recovering said first metal from said ore.
 2. The process ofclaim 1 wherein the plant derived aromatic component is lignin.
 3. Theprocess of claim 1 wherein the plant derived aromatic component haswater soluablizing groups selected from the group consisting ofsulfonate salts, phenolate salts, carboxylate salts and mixturesthereof.
 4. The process of claim 3 wherein the plant derived aromaticcomponent is selected from the group consisting of a sodiumlignosulfonate, a sodium lignin and mixtures thereof.
 5. The process ofclaim 4 wherein the plant derived aromatic component is a sodiumlignosulfonate.
 6. The process of claim 2 wherein the ortho-quinonefunctionality is present in the component in the range of from at leastabout 2 weight percent to about 30 weight percent of the total weight ofthe plant derived aromatic component.
 7. The process of claim 4 whereinthe ortho-quinone functionality is present in the component in the rangeof from at least about 2 weight percent to about 30 weight percent ofthe total weight of the plant derived aromatic component.
 8. The processof claim 1 wherein the oxidant is oxygen and the contacting is in thepresence of an aqueous medium at a pH in the range of from about 9 toabout
 13. 9. The process of claim 1 wherein the oxidant is oxygen andthe contacting is in the presence of an aqueous medium at a pH in therange of from about 9 to about
 13. 10. The process of claim 3 whereinthe oxidant is oxygen and the contacting is in the presence of anaqueous medium at a pH in the range of from about 9 to about
 13. 11. Aprocess for recovering at least one first metal selected from the groupconsisting of gold, silver, the platinum group metals and mixturesthereof from an ore comprising contacting said ore with at least oneadded plant derived aromatic component selected from the groupconsisting of lignin, and tannin and having ortho-quinone functionalitywherein the ortho-quinone functionality is present in the component inthe range of from at least about 1 weight percent to about 40 weightpercent of the total weight of the plant derived aromatic component andcyanide in the presence of an aqueous medium at an alkaline pH atconditions effective to form a gold cyanide complex, said plant derivedaromatic component being present in an aqueous soluble amount effectiveto at least promote the formation of the first metal cyanide complex andan additional oxidant being present to provide at least one of thefollowing: (1) form and cycle said plant derived aromatic componentbetween ortho-quinone and catechol oxidations states and (2) cycle saidplant derived aromatic component between ortho-quinone and catecholoxidation states and recovering said first metal from said ore.
 12. Theprocess of claim 11 wherein the plant derived aromatic component isselected from the group consisting of lignin, tannin and mixturesthereof.
 13. The process of claim 11 wherein the plant derived aromaticcomponent is selected from the group consisting of a sodiumlignosulfonate, a sodium lignin and mixtures thereof.
 14. The process ofclaim 11 wherein the ortho-quinone functionality is present in thecomponent in the range of from about 1 weight percent to about 30 weightpercent.
 15. The process of claim 11 wherein the oxidant is oxygen andthe contacting is in the presence of an aqueous medium at a pH in therange of from about 9 to about
 13. 16. The process of claim 5 whereinthe ortho-quinone functionality is present in the component in the rangeof from at least about 2 weight percent to about 30 weight percent ofthe total weight of the plant derived aromatic component.
 17. Theprocess of claim 5 wherein the oxidant is oxygen and the contacting isin the presence of an aqueous medium at a pH in the range of from about9 to about
 13. 18. The process of claim 7 wherein the oxidant is oxygenand the contacting is in the presence of an aqueous medium at a pH inthe range of from about 9 to about
 13. 19. The process of claim 13wherein the ortho-quinone functionality is present in the component inthe range of from about 1 weight percent to about 30 weight percent.